For grafting of a polymer on a surface of a solid substance, there have been attempts to produce a thick polymer brush on a solid substance surface through living radical polymerization. In this method, a polymerization initiator is immobilized on a particle surface of a solid substance beforehand, and then various monomers are polymerized to form a polymer graft chain.
For example, Patent Literature 1 and Non-Patent Literature 1 disclose using polymerization initiators that can be used for a silane coupling process against a solid substance surface. Specifically, these publications disclose a polymerization initiator (2-bromo-2-methyl)propionyloxyhexyltriethoxysilane (BHE). BHE is synthesized by hydrosilylation reaction of alkoxysilane with the double bond formed at one end of a compound having a radical polymerization initiation group at the other end of the molecular chain. However, it cannot be said that this producing method is industrially useful because the hydrosilylation reaction has only moderate reaction efficiency.
Patent Literatures 2 and 3 disclose methods of producing a silicon compound capable of initiating living radical polymerization. The methods include a hydrosilylation reaction of chlorosilane, followed by a reaction with orthoformate or alcohol to introduce an alkoxy group. The methods can improve reaction efficiency, but are problematic in that the catalysts of the hydrosilylation reaction are water prohibitive.
Rubber compositions and plastic compositions conventionally contain a reinforcing agent (or reinforcing filler as it is also called). For example, silica is contained as a reinforcing agent as a means to meet the demand for the development of a low-heat-generating rubber composition in tire applications where high fuel efficiency is required. However, silica has poor interaction with the matrix diene rubber because of the high polarity of the silica particle surface. Patent Literature 4 attempts to improve silica dispersibility with a method in which silica is coated with polymer through radical polymerization after being impregnated with a vinyl monomer.